Comment 6 for bug 905636

Thank you both.
I've investigated this further and it appears that not the delay between simulated key press and key release is at issue, it is the the mouse button press and release itself causing this. The click on onboard causes the awesome-popup to close prematurely and to subsequently miss key press events.

Inserting delays between click and key event as I suggested actually worsens the situation. On the bright side, this way I'm able to easily reproduce key strokes getting lost here too.

Sending a wole string of key strokes without intermediate clicking, e.g. as onboard's snippets do, works fine.

Hover click doesn't help as long there is still (simulated) mouse clicking involved, as is the case with mousetweaks.

To me it looks like the fix has to come from firefox. I'll look into filing a bug report.